1. Field of Invention
The invention relates to a power supply control system for a vehicle. More specifically, the invention relates to a power supply control system for a vehicle, which executes an idling stop control that automatically carries out stop and start of an engine according to an operating state of the vehicle.
2. Description of Related Art
A power supply system for a vehicle provided with a lead-acid battery and a lithium-ion battery has been known. An example of this kind of system is disclosed in Japanese Patent Laid-Open Publication No. 2001-313082, for example. This power supply system regenerates energy produced on vehicle deceleration to the lead-acid battery as well as to the lithium-ion battery, which has a higher regenerative capacity. Therefore, energy efficiency for the on-vehicle power supply system as a whole can be improved. Furthermore, in the power supply system, power is supplied to the engine from the lead-acid battery on vehicle start.
A vehicle may be equipped with a system that carries out a control which stops an operation of an engine, for example, during a traffic light stop or the like, and restarts the operation of the engine when the vehicle pulls away (this control is hereafter referred to as the “idling stop control”). In the state where the vehicle in which the idling stop control is carried out mounts the aforementioned lead-acid battery and the lithium-ion battery, and, as in the system discussed above, if both an engine start that accompanies normal vehicle start-up and an engine start that accompanies the idling stop control are carried out constantly utilizing the lead-acid battery, deterioration of the lead-acid battery will be precipitated because the lead-acid battery is in a state where it is being continuously operated under a load. Therefore, in this configuration, the reliability of the engine start is reduced and in turn it becomes increasingly possible that an opportunity to execute the idling stop control will be denied.